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Author Topic: problems with machining holes and Z axis  (Read 2542 times)

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problems with machining holes and Z axis
« on: October 08, 2017, 03:20:39 PM »
Hello all.
i'm trying to make a few bits for my motorbike and am experiencing some problems.

When the Z axis is set to zero/home and then i start the gcode, it's not calibrating prooperly, yet when i do the auoto caliberation it is perfect.
i have the units set to 400 per, yet it only moves decimals of a millimeter, if i set it to 800 it moves 2mm (which is correct as i'm trying to move it 1mm at a time), i then change it to 405 and its moving 0.9mm....if i switch the computer off and return to it it starts all over again despite keeping the 405 setting.

Also, my holes i'm trying to machine out of the centre are offset, even though they are drawn central.....they're South West by approximately 3mm.

Any help greatly appreciated.

Thank you
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?
Re: problems with machining holes and Z axis
« Reply #1 on: October 08, 2017, 03:46:46 PM »
Hi,
on your motor tuning page when you set the 'steps per' and so on are you hitting <save> as you exit?

Craig
My wife left with my best friend...
     and I miss him!
Re: problems with machining holes and Z axis
« Reply #2 on: October 08, 2017, 04:02:06 PM »
Hi Craig, thank you for the reply.
Yes i'm hitting save and when you turn off and go back to it, the steps per are as last saved (in this case 405) yet the z axis is not doing the same as it was.
The first hole is almost correct, but then the more it goes on through the code, the higher the z axis gets. When I click 'go to zero' the mill bit is approx 10mm higher than when it started but the DRO reads zero.
I got some verniers on it and it was moving 0.3mm per plunge, but DRO says 1mm.
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?
Re: problems with machining holes and Z axis
« Reply #3 on: October 08, 2017, 04:04:41 PM »
X and Y axis are spot on at 400 steps per.
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?
Re: problems with machining holes and Z axis
« Reply #4 on: October 08, 2017, 04:32:17 PM »
Hi,
if the 'steps per' are being correctly saved then calibration is not your problem. You have an issue with the Z axis.

Run some tests, without a workpiece:
<zero z>
MDI g0 z10
g0 z0
g0 z10
g0 z0
g0 z10
g0 z0

The Z axis should move up and down 10mm. Do it do so? Does it end up in exactly the same place it started? Note
I would expect the DRO to go back to zero but if the axis is faulty then it may not physically return to where it started.

Craig
My wife left with my best friend...
     and I miss him!
Re: problems with machining holes and Z axis
« Reply #5 on: October 08, 2017, 04:39:30 PM »
On the auto calibration it is spot on.
'How far do you want axis to move?'
I've typed 10mm 30mm 50mm -50mm -25mm
'How far did it move?'
It is spot on every time.
'Axis set to 400 steps per. Do you accept this?'
I click yes.
I start the job and the z axis moves 0.3mm
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?
Re: problems with machining holes and Z axis
« Reply #6 on: October 08, 2017, 05:03:35 PM »
Hi,
yes its calibrated, thats not your problem. You need to shift it up and down a small amount repeatedly to see if
the Z axis is gaining or losing steps. Leave the calibration as is and do the test I suggested.

Craig

My wife left with my best friend...
     and I miss him!
Re: problems with machining holes and Z axis
« Reply #7 on: October 08, 2017, 05:13:30 PM »
Thank you Craig.
I'll get on it tomorrow after work and let you know.
Thank you for your help.
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?
Re: problems with machining holes and Z axis
« Reply #8 on: October 09, 2017, 02:00:02 PM »
Good evening Craig,
I did your test and all was moving as it should.
What I have noticed that if i mess with the motor tuning, it starts to work something like it should???
I did a few air tests and all seems well....ish
So i thought I'd do a cut piece in MDF. The holes are still off centre, and after finishing the job, i clicked got to z, the DRO is reading zero, but the mill piece was 5mm north east of where it started from
I did the tests on the x and y axis and all is perfect with vernier gauges
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?
Re: problems with machining holes and Z axis
« Reply #9 on: October 09, 2017, 02:02:39 PM »
I have to say though, apart from the minor niggles i'm having, i am really liking the cnc, sheetcam and mach3.
if as complete novice like me can get somewhere with it all, anyone can....obviously with a little guidance  ;D
Yes, yes Mrs Lincoln,...but apart from that, did you enjoy the play?